create manually dispatched workflow for testing (wpengine#721)

.github/actions/post-release/index.js

@@ -0,0 +1,16 @@
+async function mergeToMain({github, context}) {
+  console.log("TEST: Merging canary to main...");
+
+  const result = await github.rest.repos.merge({
+      ...context.repo,
+      base: "TEST_main",
+      head: "TEST_canary",
+      commit_message: "TEST: Merge release from branch `canary` into `main`"
+  });
+
+  return result;
+}
+
+module.exports = {
+  mergeToMain
+}

.github/workflows/post-release.yml

@@ -0,0 +1,37 @@
+name: Post-release jobs
+
+on:
+  workflow_dispatch:
+    inputs:
+      published:
+        description: "Simulates whether changesets did or did not publish a release."
+        required: true
+        default: "false"
+
+jobs:
+  simulate_output:
+    name: "Simulate changesets/action output"
+    runs-on: ubuntu-latest
+    outputs:
+      published: ${{ steps.step1.outputs.published }}
+    steps:
+      - id: step1
+        run: echo "::set-output name=published::${{ github.event.inputs.published }}"
+  merge_to_main:
+    name: "Merge `canary` into `main`"
+    runs-on: ubuntu-latest
+    needs: simulate_output
+    if: ${{ needs.simulate_output.outputs.published == 'true' }}
+    steps:
+      - name: Checkout Repo
+        uses: actions/checkout@v2
+        with:
+          # This makes Actions fetch all Git history so that Changesets can generate changelogs with the correct commits
+          fetch-depth: 0
+
+      - name: Merge to main
+        uses: actions/github-script@v5
+        with:
+          script: |
+            const { mergeToMain } = require('.github/actions/post-release/index.js')
+            return await mergeToMain({github, context})